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1.
PLoS Comput Biol ; 16(12): e1008436, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-33315865

RESUMEN

A major challenge in evolutionary developmental biology is to understand how genetic mutations underlie phenotypic changes. In principle, selective pressures on the phenotype screen the gene pool of the population. Teeth are an excellent model for understanding evolutionary changes in the genotype-phenotype relationship since they exist throughout vertebrates. Genetically modified mice (mutants) with abnormalities in teeth have been used to explore tooth development. The relationship between signaling pathways and molar shape, however, remains elusive due to the high intrinsic complexity of tooth crowns. This hampers our understanding of the extent to which developmental factors explored in mutants explain developmental and phenotypic variation in natural species that represent the consequence of natural selection. Here we combine a novel morphometric method with two kinds of data mining techniques to extract data sets from the three-dimensional surface models of lower first molars: i) machine learning to maximize classification accuracy of 22 mutants, and ii) phylogenetic signal for 31 Murinae species. Major shape variation among mutants is explained by the number of cusps and cusp distribution on a tooth crown. The distribution of mutant mice in morphospace suggests a nonlinear relationship between the signaling pathways and molar shape variation. Comparative analysis of mutants and wild murines reveals that mutant variation overlaps naturally occurring diversity, including more ancestral and derived morphologies. However, taxa with transverse lophs are not fully covered by mutant variation, suggesting experimentally unexplored developmental factors in the evolutionary radiation of Murines.


Asunto(s)
Modelos Anatómicos , Diente Molar/anatomía & histología , Transducción de Señal , Animales , Evolución Biológica , Aprendizaje Automático , Ratones , Ratones Mutantes , Filogenia
2.
PLoS One ; 15(6): e0233281, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32511250

RESUMEN

Dental enamel thickness, topography, growth and development vary among hominins. In Homo, the thickness of dental enamel in most Pleistocene hominins display variations from thick to hyper-thick, while Neanderthals exhibit proportionally thinner enamel. The origin of the thin trait remains unclear. In this context, the Middle Pleistocene human dental assemblage from Atapuerca-Sima de los Huesos (SH) provides a unique opportunity to trace the evolution of enamel thickness in European hominins. In this study, we aim to test the hypothesis if the SH molar sample approximates the Neanderthal condition for enamel thickness and/or distribution. This study includes 626 molars, both original and comparative data. We analysed the molar inner structural organization of the original collections (n = 124), belonging to SH(n = 72) and modern humans from Spanish origin (n = 52). We compared the SH estimates to those of extinct and extant populations of the genus Homo from African, Asian and European origin (estimates extracted from literature n = 502). The comparative sample included maxillary and mandibular molars belonging to H. erectus, East and North African Homo, European Middle Pleistocene Homo, Neanderthals, and fossil and extant H. sapiens. We used high-resolution images to investigate the endostructural configuration of SH molars (tissue proportions, enamel thickness and distribution). The SH molars exhibit on average thick absolute and relative enamel in 2D and 3D estimates, both in the complete crown and the lateral enamel. This primitive condition is shared with the majority of extinct and extant hominin sample, except for Neanderthals and some isolated specimens. On the contrary, the SH molar enamel distribution maps reveal a distribution pattern similar to the Neanderthal signal (with thicker enamel on the lingual cusps and more peripherally distributed), compared to H. antecessor and modern humans. Due to the phylogenetic position of the SH population, the thick condition in molars could represent the persistence of the plesiomorphic condition in this group. Still, more data is needed on other Early and Middle Pleistocene populations to fully understand the evolutionary meaning of this trait.


Asunto(s)
Fósiles/anatomía & histología , Hominidae/anatomía & histología , Diente Molar/anatomía & histología , Animales , Evolución Biológica , Esmalte Dental/anatomía & histología , Esmalte Dental/metabolismo , Humanos , Diente Molar/metabolismo , Hombre de Neandertal , Filogenia , España , Diente , Corona del Diente/anatomía & histología , Corona del Diente/metabolismo
4.
Braz Oral Res ; 34: e039, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32374813

RESUMEN

To compare the shaping ability of different single-file systems in the preparation of mesial curved canals of mandibular molars using micro-CT technology. Fifteen mesial roots of mandibular molars with two independent and curved canals (n = 30) were selected, scanned at a resolution of 26.7 µm anatomically matched, and distributed into three groups (n = 10), according to the preparation system: WaveOne 25.08, Reciproc 25.08, and OneShape 25.06. A final micro-CT scanning was performed, data sets were registered with their respective counterparts, and compared regarding the three-dimensional (volume, surface area, and structure model index - SMI) and two-dimensional (perimeter, area, roundness, major and minor diameters) parameters, as well as, canal transportation, using ANOVA and post hoc Tukey tests (α = 5%). Overall, no difference was observed between groups regarding area, perimeter, volume, surface area, and canal transportation (p > 0.05). Within group, no canal transportation was significantly higherobserved in the apical third (0.10 ± 0.05 mm) compared to coronal (0.08±0.040 mm) and middle (0.07 ± 0.03 mm) thirds (p < 0.05). Structure model index (SMI) was statistically higher after preparation with OneShape instrument (0.36 ± 0.26) compared to other systems (p < 0.05). Within the parameters of this study, similar shaping ability was observed in the preparation of mesial curved root canals of mandibular molars with Reciproc, OneShape and WaveOne systems.


Asunto(s)
Cavidad Pulpar/anatomía & histología , Cavidad Pulpar/diagnóstico por imagen , Preparación del Conducto Radicular/instrumentación , Análisis de Varianza , Instrumentos Dentales , Diseño de Equipo , Humanos , Ensayo de Materiales , Diente Molar/anatomía & histología , Valores de Referencia , Estadísticas no Paramétricas , Microtomografía por Rayos X/métodos
5.
Artículo en Inglés | MEDLINE | ID: mdl-32466156

RESUMEN

The purpose of the presented Artificial Intelligence (AI)-tool was to automatically segment the mandibular molars on panoramic radiographs and extract the molar orientations in order to predict the third molars' eruption potential. In total, 838 panoramic radiographs were used for training (n = 588) and validation (n = 250) of the network. A fully convolutional neural network with ResNet-101 backbone jointly predicted the molar segmentation maps and an estimate of the orientation lines, which was then iteratively refined by regression on the mesial and distal sides of the segmentation contours. Accuracy was quantified as the fraction of correct angulations (with predefined error intervals) compared to human reference measurements. Performance differences between the network and reference measurements were visually assessed using Bland-Altman plots. The quantitative analysis for automatic molar segmentation resulted in mean IoUs approximating 90%. Mean Hausdorff distances were lowest for first and second molars. The network angulation measurements reached accuracies of 79.7% [-2.5°; 2.5°] and 98.1% [-5°; 5°], combined with a clinically significant reduction in user-time of >53%. In conclusion, this study validated a new and unique AI-driven tool for fast, accurate, and consistent automated measurement of molar angulations on panoramic radiographs. Complementing the dental practitioner with accurate AI-tools will facilitate and optimize dental care and synergistically lead to ever-increasing diagnostic accuracies.


Asunto(s)
Inteligencia Artificial , Diente Molar , Radiografía Panorámica , Odontólogos , Humanos , Diente Molar/anatomía & histología , Diente Molar/crecimiento & desarrollo , Rol Profesional
6.
Niger J Clin Pract ; 23(4): 534-538, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32246661

RESUMEN

Objectives: To study the prevalence of middle mesial and middle distal canals in permanent mandibular molars in Egyptian subpopulation using micro-computed tomography. Materials and Methods: Two hundred and forty extracted mandibular permanent molars of Egyptian patients were scanned using micro-computed tomography, then the images were reconstructed to allow for the detection of the middle mesial (MM) and middle distal (MD) canals of the molars examined. The path of each extra canal was studied to determine the configuration of each canal. Data were analyzed statistically using the Chi-square test with a level of significance set at P< 0.05. Results: The evaluation of three-dimensional (3D) images of this study showed that no significant difference was found between the percentage of MM (27.5%) and MD canals (22.5%) (P = 0.2064); however, there was a significant difference between the percentage of teeth having both extra canals (10%) and teeth having only one of these canals (P < 0.05). The confluent configuration (71%) was significantly higher than the other configurations (P < 0.05). Conclusion: A higher percentage of MM canal was detected followed by the MD canal. The least significant was both canals occurring within the same molar. The percentage of the confluent configuration was the highest. The apt knowledge of the variations of the root canal system anatomy and the respect of the discrepancies associated with diverse demographic areas will ensure the proper management of each tooth with endodontic involvement and its long-term success.


Asunto(s)
Diente Molar/anatomía & histología , Tratamiento del Conducto Radicular , Raíz del Diente/anatomía & histología , Estudios Transversales , Egipto/epidemiología , Humanos , Mandíbula/anatomía & histología , Tratamiento del Conducto Radicular/efectos adversos , Tratamiento del Conducto Radicular/estadística & datos numéricos
7.
J Appl Oral Sci ; 28: e20190168, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32236352

RESUMEN

INTRODUCTION: Isthmuses are reported as common anatomic complexities in teeth often associated with failures in endodontic treatment. They should be considered before starting treatment and a preoperative computed tomography scan (CT) may demonstrate these complexities. OBJECTIVE: To assess the diagnostic value of the highest resolution settings of a cone-beam CT (CBCT) system in identifying and measuring apical isthmuses, using micro-CT as reference. METHODOLOGY: After micro-CT scanning, 40 humans' lower first molars with isthmuses in the apical-3 mm of mesial roots were scanned by the highest resolution settings of the New Generation i-Cat ® CBCT equipment. Two blinded observers recorded the detection of isthmuses in CBCT scans. The lengths of isthmuses were compared between micro-CT and CBCT to assess the diagnostic value of CBCT. Quantitative data for sensitivity were represented as percentages (95% confidence interval). The Bland-Altman method was used to assess differences between gold standard lengths (micro-CT) and CBCT lengths. RESULTS: BCT demonstrated 30 positive findings, representing sensitivity for isthmus identification of 75% (95% CI=0.4114-1.1364). Differences between the lengths in micro-CT (1.99±0.40 mm) and CBCT (1.53±0.41 mm) were significant (p<0.0001). CONCLUSION: The CBCT device used presented limited diagnostic value in the identification and measurement of apical isthmuses in the mesial roots of lower molars. In some cases, the actual anatomy of the apical root canal may not be completely delineated in this type of CBCT system, even using the highest resolution settings.


Asunto(s)
Tomografía Computarizada de Haz Cónico/métodos , Ápice del Diente/anatomía & histología , Ápice del Diente/diagnóstico por imagen , Raíz del Diente/anatomía & histología , Raíz del Diente/diagnóstico por imagen , Análisis de Varianza , Humanos , Diente Molar/anatomía & histología , Diente Molar/diagnóstico por imagen , Variaciones Dependientes del Observador , Tamaño de los Órganos , Valores de Referencia , Reproducibilidad de los Resultados , Tratamiento del Conducto Radicular/métodos , Sensibilidad y Especificidad
8.
Niger J Clin Pract ; 23(2): 232-239, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-32031099

RESUMEN

Aims: To evaluate the prevalence, correlation, and differences of C-shaped canal morphology in mandibular premolars and molars by means of cone-beam computed tomography (CBCT). Materials and Methods: A total of 1433 mandibular premolars and molars CBCT scans from the Saudi population were evaluated. Axial sections of the roots were acquired at coronal, middle, and apical levels to evaluate C-shaped canals types. The prevalence, correlation, differences of C-shaped canals, bilateral/unilateral presence, gender differences, and location of external grooves on roots were assessed. Results: The prevalence of C-shaped canals in the first premolars was 1.5%, 0.80% in second premolars and 7.9% in second molars, whereas C-shaped canals were absent in first molars. No correlation was found between the presence of C-shaped canals within premolars and molars and between the two groups in the same individual. Both premolars and molars exhibited different types of C-shaped canals, C2 being predominant in premolars and C3 in second molars. Longitudinal external grooves were mostly located on mesiolingual (ML) surface in premolars and lingual in molars. Females showed more prevalence of C-shaped canals in second molars and no differences in premolars. Bilateral symmetry and unilateral presence in premolars and second molars were not significant. Conclusions: Although the prevalence of C-shaped canals is significantly higher in mandibular second molars, they are also found in mandibular premolars but in small percentages. No significant differences were found between both genders and both sides. Since they exhibit unpredictable morphology and differences across the root length, the use of small field CBCT is recommended when such anatomy is presented in a tooth indicated for root canal treatment for better management.


Asunto(s)
Diente Premolar/diagnóstico por imagen , Tomografía Computarizada de Haz Cónico/métodos , Cavidad Pulpar/diagnóstico por imagen , Mandíbula/diagnóstico por imagen , Diente Molar/diagnóstico por imagen , Raíz del Diente/diagnóstico por imagen , Adolescente , Adulto , Diente Premolar/anatomía & histología , Estudios Transversales , Cavidad Pulpar/anatomía & histología , Femenino , Humanos , Masculino , Mandíbula/anatomía & histología , Persona de Mediana Edad , Diente Molar/anatomía & histología , Prevalencia , Arabia Saudita , Factores Sexuales , Raíz del Diente/anatomía & histología , Adulto Joven
9.
BMC Oral Health ; 20(1): 43, 2020 02 06.
Artículo en Inglés | MEDLINE | ID: mdl-32028960

RESUMEN

BACKGROUND: Better understanding of the danger zone anatomy in mesial roots (MRs) of mandibular first molars (MFMs) may serve to decrease the risk of mishaps. This study aimed to measure the minimal distal dentine thicknesses of danger zone in MRs of MFMs in a native Chinese population using cone-beam computed tomography (CBCT). METHODS: CBCT images of 1792 MFMs from 898 Chinese patients were analyzed. The minimal distal dentine thicknesses of the mesiobuccal (MB) and mesiolingual (ML) canals below the furcation 1, 2, 3, 4, 5 mm were measured. The association between the minimal distal dentine thicknesses and the root lengths, patient's age and gender, side were assessed. RESULTS: The minimal distal dentine thicknesses of MB and ML canals are located 3 ∼ 4 mm below the furcation for both men and women. There are no differences between MB and ML canals, while the minimal distal dentine thicknesses of MB and ML canals were higher in men than women (P < 0.05), except at 1 and 3 mm of ML canals (P > 0.05). The minimal distal dentine thicknesses of MB and ML canals increased with age in both men and women at each location (P < 0.05). The minimum distal dentine thickness at every location were significantly different between long teeth and short teeth both in men and women (P < 0.05), with short teeth having the smallest mean values. There are no significant differences between two sides (P > 0.05). CONCLUSIONS: The minimal distal dentine thicknesses of MRs in MSMs have close correlation with root length, patient's age and gender.


Asunto(s)
Cavidad Pulpar/anatomía & histología , Dentina/anatomía & histología , Mandíbula/diagnóstico por imagen , Diente Molar/anatomía & histología , Raíz del Diente/anatomía & histología , Adolescente , Adulto , China , Tomografía Computarizada de Haz Cónico , Cavidad Pulpar/diagnóstico por imagen , Femenino , Humanos , Masculino , Persona de Mediana Edad , Diente Molar/diagnóstico por imagen , Raíz del Diente/diagnóstico por imagen
10.
Int. j. morphol ; 38(1): 126-128, Feb. 2020. tab
Artículo en Inglés | LILACS | ID: biblio-1056409

RESUMEN

The current International Terminologia Anatomica is written in latin and from it, the translation into the corresponding language is carried out. There are terms of greek origin that sometimes do not fully describe the anatomical structure. In this context, the mylos root, present in mylohyoid word, is defined in greek " like a mill" or "resembling a tooth". However, this definition does not accurately represent the mylohyoid structures that it describes. Therefore the question arises: is the mylos root the most appropriate one for naming these structures?.


La actual Terminologia Anatomica (TA), se encuentra redactada en latín y a partir de ella se realiza la traducción al idioma correspondiente. Existen en ella términos de origen griego que en ocasiones no describen a cabalidad la estructura anatómica. En este contexto la raíz mylos, presente en milohioideo(a), se define en griego "como de un molino" o "semejante a una muela", sin embargo, esta definición no precisa las estructuras milohioideas que se desean describir. Entonces surge la interrogante, ¿es la raíz mylos la más adecuada para denominar esas estructuras?.


Asunto(s)
Humanos , Mandíbula/anatomía & histología , Diente Molar/anatomía & histología , Terminología como Asunto
11.
Sci Rep ; 10(1): 1247, 2020 01 27.
Artículo en Inglés | MEDLINE | ID: mdl-31988399

RESUMEN

The purpose of this study was to evaluate the incidence and microscopic anatomy of the isthmus to provide more precise anatomical information about the mesiobuccal (MB) roots of the maxillary first molars and the mesial (M) roots of the mandibular first molars. Twenty-eight maxillary and 31 mandibular first molars were embedded, sectioned, stained, and observed at 30× magnification to evaluate the incidence and microscopic anatomy of the isthmus. The incidence of an isthmus 3 mm from the apex was 89.3% and 100% in the MB roots of the maxillary first molars and in the M roots of the mandibular first molars, respectively. The mean dentin thickness between the isthmus and the distal root surface was <1 mm at a distance of 3 mm from the apex in both types of roots. In this study, whenever two main canals were located in the MB roots of the maxillary first molars and in the M roots of the mandibular first molars, the likelihood of the presence of an isthmus increased. Therefore, clinicians should be aware of the thinnest dimensions in the distal surface of the MB roots of the maxillary first molars and the M roots of the mandibular first molars during nonsurgical and surgical root canal treatment.


Asunto(s)
Cavidad Pulpar/anatomía & histología , Diente Molar/anatomía & histología , Raíz del Diente/anatomía & histología , Adulto , Dentina/anatomía & histología , Femenino , Humanos , Masculino , Microscopía/métodos , Odontometría , República de Corea/epidemiología , Ápice del Diente/anatomía & histología
12.
Niger J Clin Pract ; 23(1): 79-83, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31929211

RESUMEN

Objectives: The aim of this study was to evaluate the quantity of apically extruded debris after canal shaping with three single-file systems. Materials and Methods: Sixty mesiobuccal canals of mandibular molars were divided into three experimental groups according to the used file systems-WaveOne Gold, RECIPROC Blue, and HyFlex EDM One file. Debris extruded during canal shaping were collected in preweighed vials. Each canal was irrigated with 5 mL of distilled water via a 30 G side-vented needle. The amount of the debris extruded from each canal was calculated by subtracting the preinstrumentation from postinstrumentation measurement. The preparation times were recorded. Data were analyzed using analysis of variance (ANOVA) and posthoc Tukey tests with α = 0.05. Results: WaveOne Gold extruded the least amount of debris. Results between WaveOne Gold and HyFlex EDM were significantly different. No significant differences in canal shaping time were detected among the three groups (P > 0.05). Conclusion: WaveOne Gold showed the best results regarding apical debris extrusion. Difference between WaveOne Gold and HyFlex EDM suggests that file design and motion kinematics affect the quantity of debris extrusion.


Asunto(s)
Cavidad Pulpar/cirugía , Preparación del Conducto Radicular/instrumentación , Ápice del Diente/cirugía , Fenómenos Biomecánicos , Cavidad Pulpar/anatomía & histología , Diseño de Equipo , Humanos , Diente Molar/anatomía & histología , Diente Molar/cirugía , Preparación del Conducto Radicular/métodos
13.
PLoS One ; 15(1): e0227001, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-31923224

RESUMEN

Crown shape variation of the first lower molar in the arctic (Vulpes lagopus) and red foxes (Vulpes vulpes) was analyzed using five groups of morphotypes. Carnassial morphologies were compared between the species and between spatially and temporally distant populations: one Late Pleistocene (n = 45) and seven modern populations of the arctic fox (n = 259), and one Late Pleistocene (n = 35) and eight modern populations of the red fox (n = 606). The dentition of Holocene red foxes had larger morphotype variability than that of arctic foxes. The lower carnassials of the red fox kept have some primitive characters (additional cusps and stylids, complex shape of transverse cristid), whereas the first lower molars of the arctic fox have undergone crown shape simplification, with the occlusal part of the tooth undergoing a more pronounced adaptation to a more carnivorous diet. From the Late Pleistocene of Belgium to the present days, the arctic fox's crown shape has been simplified and some primitive characters have disappeared. In the red fox chronological changes in the morphology of the lower carnassials were not clearly identified. The phyletic tree based on morphotype carnassial characteristics indicated the distinctiveness of both foxes: in the arctic fox line, the ancient population from Belgium and recent Greenland made separate branches, whereas in the red foxes the ancient population from Belgium was most similar to modern red foxes from Belgium and Italy.


Asunto(s)
Carnivoría , Zorros , Diente Molar/anatomía & histología , Animales , Regiones Árticas , Bélgica , Groenlandia , Historia del Siglo XXI , Historia Antigua , Italia , Filogenia , Especificidad de la Especie
14.
Arch Oral Biol ; 110: 104603, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31835191

RESUMEN

OBJECTIVE: The aim of this study was to assess whether analyzed groups from two historical periods: Late Medieval (LMP), and Modern (MP) from Radom varied in the number of tooth roots and root canal system morphology. METHODS: Root morphology of 229 permanent human teeth were analyzed using Cone Beam Computed Tomography. Additionally, the mitochondrial DNA (mtDNA) of 29 individuals from the LMP and 31 from the MP was analyzed. RESULTS: In LMP, the maxillary first premolars were dominated by one root, while in MP second and third roots also appeared. Maxillary first molars in LMP presented three roots, while two-rooted forms occurred in MP. All mandibular first molars from the LMP and almost all (98%) from MP presented two roots. The greatest diversity in terms of root canal number occurred in one-rooted maxillary first premolars, the mesiobuccal root of the maxillary first molars, and the mesial and distal roots of the mandibular first molars in both groups. A few haplogroups from outside Europe (C, N, and R) were recorded in the MP Radom population. Moreover, this population had substantially higher haplogroup diversity compared with the LMP population. CONCLUSION: Odontological research indicates an increase in the diversity in the number of roots and the shape of root canals in MP. This information corresponds to genetic research, which also indicates an increase in the diversity of haplogroups during the MP.


Asunto(s)
Cavidad Pulpar , Diente Molar , Antropología , Diente Premolar , Tomografía Computarizada de Haz Cónico , Cavidad Pulpar/anatomía & histología , Europa (Continente) , Humanos , Diente Molar/anatomía & histología , Raíz del Diente
17.
Gen Dent ; 68(1): 66-71, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-31859666

RESUMEN

Knowledge of the anatomical relationships between the maxillary sinus (MS) and posterior teeth is important to prevent complications when endodontic or oral surgical procedures are performed. The aim of this study was to evaluate the relationships between the root apices of maxillary posterior teeth and the MS floor. Three oral radiologists evaluated 851 posterior teeth (1969 roots) imaged with cone beam computed tomography. The roots were analyzed individually in parasagittal sections, on which the most superior point of the apex was observed. A qualitative evaluation was performed, and each root was assigned a proximity score: 1, root invaginating the MS; 2, root in close contact with the MS floor; 3, root with no relationship with the MS; and 4, root with a measurable proximity to the MS. For roots classified as score 4, the distance to the MS floor was measured (quantitative analysis). Student t tests, 1-way analysis of variance, and simple linear regression analysis were performed (P < 0.05). The qualitative analysis revealed that the mesiobuccal root of the second molar had a pronounced proximity to the MS. The quantitative analysis revealed no differences in distance to the MS between right and left posterior teeth or between the different roots of the same tooth. In relation to the MS, the second molar was positioned closest, followed by the first molar, second premolar, and first premolar. Except for the comparison between mean distances of the second premolar and first molar (P = 0.11), the differences between groups of teeth were statistically significant (P < 0.05). Simple linear regression analysis showed that the more posterior the tooth was in relation to the midline, the shorter the mean distance from the root apex to the MS floor (P < 0.05). The mesiobuccal roots of second molars were closest to the MS. Second molars exhibited the shortest distances between their root apices and the MS and the greatest number of roots that were invaginating or in close contact with the MS. Therefore, second molars require special attention when endodontic or oral surgical approaches involve those regions.


Asunto(s)
Tomografía Computarizada de Haz Cónico/métodos , Maxilar , Seno Maxilar , Humanos , Procesamiento de Imagen Asistido por Computador , Maxilar/anatomía & histología , Seno Maxilar/anatomía & histología , Seno Maxilar/diagnóstico por imagen , Diente Molar/anatomía & histología , Diente Molar/diagnóstico por imagen , Raíz del Diente/anatomía & histología , Raíz del Diente/diagnóstico por imagen
18.
Am J Phys Anthropol ; 171(1): 76-88, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31710703

RESUMEN

OBJECTIVES: Here, we quantify and compare the cross-sectional shape of the mandibular corpus between M1 and M2 during growth in Pan paniscus, Pan troglodytes, and Pongo pygmaeus. The goal is to assess the hypothesis that the shape of the corpus is influenced by the development of permanent molars in their crypts, by examining ontogenetic changes in corpus shape and investigating covariation between corpus shape and M2 and M3 molar crypt forms. MATERIALS AND METHODS: Ontogenetic changes in mandibular corpus shape were assessed using landmarks and semilandmarks, and measurements of length, width, and height were used to quantify molar crypts (M2 and M3 ). Ontogenetic changes in corpus growth from the eruption of M1 to the eruption of M3 were evaluated for each species through generalized Procrustes analysis and principal components analysis in shape-space and form-space. The relationship between corpus shape and molar crypt form was investigated at three different developmental stages using two-block partial least squares (2B-PLS) analysis. RESULTS: The results show clear differences in growth patterns among all three species and provide evidence that species-level differences in mandibular corpus growth occur prior to the emergence of M1 . The results of the 2B-PLS analysis reveal that significant covariance between corpus shape and molar crypt form is limited to the developmental stage marked by the emergence of M1 , with covariance between corpus shape and M2 crypt width. Corpora that are relatively narrower in the inferior portion of the cross section covary with relatively narrower M2 crypts. CONCLUSIONS: These results have important implications for understanding the taxonomic and phylogenetic significance of mandibular corpus shape variation in the hominoid fossil record.


Asunto(s)
Mandíbula/crecimiento & desarrollo , Diente Molar/crecimiento & desarrollo , Pan paniscus/crecimiento & desarrollo , Pan troglodytes/crecimiento & desarrollo , Pongo pygmaeus/crecimiento & desarrollo , Animales , Mandíbula/anatomía & histología , Diente Molar/anatomía & histología , Pan paniscus/anatomía & histología , Pan troglodytes/anatomía & histología , Pongo pygmaeus/anatomía & histología , Especificidad de la Especie
19.
Anat Sci Int ; 95(1): 126-133, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31654329

RESUMEN

The purpose of this study was to determine the long axes of molars with multiple roots through ordinary least squares regression (LSR) and to compare them with the axes defined by principal component analysis (PCA). Three-dimensional radiological images of 20 dry skulls were obtained by cone-beam computed tomography (CBCT). Data from maxillary and mandibular first molars were extracted from the CBCT DICOM data with a three-dimensional image visualization system. The obtained data were reconstructed, converted to STL files, and three-dimensional coordinate values were extracted. The long axes were estimated by an algorithm to synchronize the LSR line with the horizontal axis which was translated to the vertical axis. The axes of the molars defined by LSR were compared with the axes of the molars defined by PCA. The coordinate point number of each molar was 5400-5800. The algorithm for determining the tooth axes in this study consisted of four stages containing three steps each. The distance between the two axes calculated by the two methods (LSR and PCA) on the horizontal plane through the origin was less than 10-12 mm and the deviations between them were less than 0.003°. The long axes of the molars estimated by LSR agree almost exactly with the axes estimated by PCA, and the accuracy is sufficient for clinical usage; however, the distance between them would shorten with a more severe convergence condition of the α value at each stage of this LSR system.


Asunto(s)
Imagenología Tridimensional/métodos , Mandíbula , Maxilar , Diente Molar/anatomía & histología , Humanos , Diente Molar/diagnóstico por imagen , Análisis de Regresión
20.
Surg Radiol Anat ; 42(1): 15-21, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31659406

RESUMEN

PURPOSE: To evaluate the internal anatomy of paramolar tubercles (PTs) on molars, determine the existence of root canals in these structures that either communicate with or are isolated from the main root canals of teeth, and analyze the prevalence of root fusion and a C-shaped canal configuration using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Twenty-six molars with PTs from the study group and 664 molars without PTs from the control group were evaluated using CBCT. The locations and sizes of tubercles were noted. The existence of root canals in PTs was detected. All teeth were evaluated according to the presence or absence of root fusion and a C-shaped canal configuration. Statistical analyses were performed with Pearson Chi square and Fisher's exact tests (p < 0.05). RESULTS: Eleven (42.3%) PTs with their own canals communicated with the main root canals of teeth, and 10 of 11 PTs (90.9%) were larger than 4 mm in size. No PT possessed its own canal independent from the other canals. Teeth with PTs tended to have more root fusions than teeth without PTs. A statistically significant correlation was observed between PTs and the C-shaped canal configuration (p < 0.01). Maxillary second molars with PTs were the major teeth showing variations in the internal morphology. CONCLUSIONS: PTs are an uncommon anatomical variation that is specific to the coronal and radicular morphology. Therefore, clinicians should be aware of its unpredictable and complex internal anatomy, particularly in cases requiring endodontic treatment. CBCT is recommended for teeth with PTs, particularly maxillary second molars, to improve the prognosis of the teeth.


Asunto(s)
Cavidad Pulpar/anatomía & histología , Cavidad Pulpar/diagnóstico por imagen , Diente Molar/anatomía & histología , Diente Molar/diagnóstico por imagen , Raíz del Diente/anatomía & histología , Raíz del Diente/diagnóstico por imagen , Adulto , Variación Anatómica , Tomografía Computarizada de Haz Cónico , Femenino , Humanos , Masculino , Adulto Joven
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